1. Field of the Invention
The present invention relates to optoelectronic devices which include electrodes and optical waveguides as essential constituent elements and, more particularly, to an electrode structure of laser diodes and their application technology.
2. Description of Related Art
There is a DFB (distributed feedback) laser as one type of laser diodes. This laser diode has a diffraction grating in which a refractive index is changed periodically along the waveguide. The laser diode can oscillate in a single longitudinal mode (SLM) (i.e., one oscillation line) around the Bragg wavelength determined by the period of the diffraction grating. For 6. In this mesa electrode structure, in order to reduce a junction area, the p-side electrode 20 must be formed on the top of a mesa stripe 25 surrounding the active layer and also must be connected to a bonding pad 27 on the thick SiO2 film 26, while taking account of step-recoverage.
As described above, in the laser diode in the related art, several stages of the epitaxial crystal growth by the MOCVD (Metal Organic Chemical Vapor Deposition) technique must be needed (growing steps (1) to (4) in the above related art), and also step-recovering processes, etc. must be needed to form the electrode.
Like the above, in the laser diode having an optical waveguide structure according to the related art, a number of manufacturing steps are needed since the device requires a complicated structure. Especially, there are problems such that its yield becomes lower and its cost increases higher because a plurality of delicate manufacturing procedures like the epitaxial crystal growth have reliability problems at regrowth interfaces. In addition, in the device structure in the related art, restrictions are imposed upon design of the optical waveguide and the electrode, and therefore it is difficult to improve the performance of the device according to the related art.